JPS61118581A - Cocoon type rotor for supercharger - Google Patents

Abstract

PURPOSE:To reduce differences of thermal expansion among blade portions in respective radial directions thereof as temperature rises and prevent volume effect from being lowered by changing wall thickness of a peripheral wall part surrounding an inner piece of a rotor blade to the thinnest one at the tip end of the blade while to thinner ones as the blade goes away from the tip end. CONSTITUTION:A coefficient of actual thermal expansion of a blade 34 in a radial direction thereof becomes greater as a value yielded by dividing wall part 48 of the blade 34 in the same direction 34 by that of an inner piece 46 is more increased while it becomes smaller as said value is more reduced. Accordingly, provided the thickness of the peripheral wall part 48 is set to get thinnest at the tip end of the blade 34 while it set to be increased as the blade goes away from the tip end, differences of thermal expansion among blade portions in respective radial directions of the rotor 10 upon temperature rise can be reduced and allowed to keep them substantially unchanged. As a result, a change of clearance between two rotors 10 can be reduced to what extent the temperature in concern and phase of rotation of the rotor 10 vary for satisfactorily preventing volume efficiency of the rotor blade upon temperature rise from being lowered.

Description

TECHNICAL FIELD The present invention relates to a cocoon-shaped rotor used in a supercharger whose housing is made of aluminum.

Prior art and its problems A supercharger supercharges air to an engine by rotating a pair of rotors with a plurality of blades at the same speed in opposite directions within a housing. Cocoon-shaped rotors each having two blades are used as rotors.

In recent years, superchargers with a pair of cocoon-shaped rotors have been made of aluminum (or more accurately, aluminum alloy) to reduce weight! ! However, when the casing is made of aluminum, the temperature inside the housing changes over a wide temperature range from room temperature to high temperature as the rotor rotates. Since there is a temperature difference between the rotor and the housing, there are disadvantages when the rotor is made of either steel or aluminum.

If the rotor is made of steel, the coefficient of thermal expansion of the rotor is significantly smaller than that of the housing;
At high temperatures, the amount of radial expansion of the rotor becomes significantly smaller than the amount of expansion of the housing in the radial direction of the rotor, and the clearance between the outer circumferential surfaces of each rotor and between the outer circumferential surface of each rotor and the inner circumferential surface of the housing decreases. As a result, there was a problem in that the volumetric efficiency decreased. Further, in this case, since the inertial mass of the rotor is large, the start-up of rotation is slow, and when the electromagnetic clutch is used for 0N10FF control, there is a problem that the durability of the electromagnetic clutch is deteriorated.

On the other hand, when the rotor is made of aluminum, if the clearance between the two rotors and the housing is set narrow when the rotor rotates at medium to low speeds and at low temperatures,
At high temperatures when the rotor rotates at high speed, the temperature difference between the housing and rotor increases, reducing each clearance and causing interference between the rotors and the housing.
On the other hand, if each clearance is set to avoid interference at high temperatures, there is a problem in that each clearance becomes thick at medium and low temperatures (as a result, the volumetric efficiency decreases).

Means for Solving the Problems Against this background, the present invention provides a cocoon-shaped rotor used in a supercharger whose housing is made of aluminum, without causing interference between both rotors and the housing, and in which the rotor This was done in order to provide a rotor that can maintain good volumetric efficiency over a wide range of changes in the temperature inside the housing that changes with the rotation of the aluminum cocoon-shaped rotor. (2) (A through hole is formed in each of the blades of II parallel to the rotation center line of the rotor, and a cylindrical inner piece made of a material with a coefficient of thermal expansion smaller than that of aluminum is tightly fitted into each of the through holes. In addition, the value obtained by dividing the wall thickness of the peripheral wall surrounding the inner piece of the blade by the wall thickness of the inner piece is smallest at the part of the blade farthest from the rotation center line of the rotor, and increases as the distance from that part increases. The reason is that it was made to grow.

Function and Effect If a through hole is formed in each blade of a cocoon-shaped rotor made of aluminum and a cylindrical inner piece is tightly fitted into the through hole, the peripheral wall surrounding the inner piece of each blade will be elastically expanded. , the external shape is determined in that state. When the temperature of the rotor rises, both the inner piece and the peripheral wall of the blades expand thermally, but since the inner piece is made of a material with a smaller coefficient of thermal expansion than aluminum, the amount of thermal expansion of the inner piece is The amount of thermal expansion is smaller than the amount of thermal expansion of the peripheral wall of the blade, and the elastic expansion of the peripheral wall of the blade is compensated by that amount. Therefore, the amount of expansion in each blade of the rotor is smaller than when the inner piece is not tightly fitted.

In other words, by forming a through hole in each blade of a cocoon-shaped rotor made of aluminum and tightly fitting a cylindrical inner piece into the through hole, the effective coefficient of thermal expansion in the rotor's radial direction can be made smaller than that of aluminum. Therefore, while setting the clearance between each rotor and the housing at medium and low temperatures to a state with good volumetric efficiency, it is possible to prevent interference between them due to the difference in temperature rise between the rotor and the housing at high temperatures. This makes it possible to avoid problems in a good manner.

However, as mentioned above, in a cocoon-shaped rotor in which the inner piece is simply tightly fitted, the clearance between the rotor and the housing remains approximately constant over the entire range of temperature changes in the housing and over all rotational phases of the rotor. However, the clearance between the loaves may vary depending on the rotational phase of the rotor when the temperature increases, and therefore the volumetric efficiency may decrease at high temperatures. The clearance between the rotor and the housing is kept constant regardless of the rotational phase of the rotor once the longitudinal length of the rotor is determined, so the effective coefficient of thermal expansion in this longitudinal direction is equal to the coefficient of thermal expansion of the housing. If set to match,
The size of the rotor remains approximately constant over the entire rotational phase of the rotor and the entire temperature range within the housing, but the clearance between the rotors is determined by the fact that the wall thickness of the rotor varies depending on the phase, and that the clearance between the rotors Because the coefficient of thermal expansion differs, the size differs depending on the rotational phase of the rotor. Therefore, if the inner piece is simply tightly fitted, the clearance size will differ depending on the rotational phase of the rotor at high temperatures. Therefore, the volumetric efficiency may decrease.

Therefore, in order to eliminate such problems, the present invention further provides that the value obtained by dividing the wall thickness of the peripheral wall surrounding the inner piece of the rotor blade by the wall thickness of the inner piece is determined by the rotation of the rotor of each blade. The blade is smallest at the point farthest from the center line, and increases as you move away from that point; in other words, it is smallest at the tip of the blade, and increases as you move away from there.

The amount of elastic expansion of each part of the peripheral wall surrounding the inner piece of the blade varies depending on the ratio of the thickness of the peripheral wall in the radial direction of the blade to the thickness of the inner piece. The smaller the value divided by the wall thickness of the piece, the larger it becomes. In addition, when the rotor temperature rises, the amount of elastic expansion of each part of the peripheral wall of the blade is relaxed based on the difference in the coefficient of thermal expansion between the blade and the inner piece. It gets bigger. In other words, the effective coefficient of thermal expansion of a blade in the radial direction increases as the value obtained by dividing the wall thickness of the peripheral wall of the blade in the radial direction by the wall thickness of the inner piece (on the contrary, the smaller the value), It becomes smaller.

Therefore, as mentioned above, the value obtained by dividing the thickness of the peripheral wall surrounding the inner piece of the blade by the thickness of the inner piece is smallest at the tip of the blade, and increases as the distance from there increases. By determining the wall thickness of the rotor, not only will the effective coefficient of thermal expansion of each blade in all radial directions be smaller than that of aluminum, but also the effective coefficient of thermal expansion in each direction extending radially from the rotor's center of rotation. It is smallest in the longitudinal direction of the rotor, and becomes larger in the direction in which the angle increases from there.

On the other hand, the length of each rotor part in the radial direction of the cocoon-shaped rotor is the longest in the longitudinal direction of the rotor (and becomes shorter in the direction from which the angle increases).

In other words, if the value obtained by dividing the wall thickness of the peripheral wall surrounding the inner piece of the blade of the cocoon-shaped rotor by the wall thickness of the inner piece satisfies the above condition, then the heat in each radial direction of the rotor when the temperature rises is This makes it possible to reduce the difference in the amount of expansion and keep their size almost constant.
By setting the sum of the thermal expansion in the radial direction of the two rotors in a pair to be as equal as possible to the thermal expansion of the distance between the rotors' axes, changes in the clearance between the two rotors can be controlled by temperature and rotor changes. This can be reduced regardless of changes in the rotational phase, and it is possible to effectively prevent a decrease in volumetric efficiency when the temperature rises.

Embodiments Hereinafter, two or three embodiments of the present invention will be explained in detail based on the drawings.

3 and 4 are a front sectional view and a side sectional view showing a supercharger equipped with a pair of cocoon-shaped rotors 10 according to the present invention. In these figures, 12 is a housing with a coefficient of thermal expansion of 2.15 to 2.34
It is made of about 10-' aluminum (more precisely, an aluminum alloy). A partition wall 18 is provided in the housing 12 and forms a rotor chamber 16 between the partition wall 18 and one side wall 14, and a bearing 2 is provided between the partition wall 18 and the side wall 14.
The two rotating shafts 24 and 26 are arranged parallel to each other and are rotatably supported at both ends via 0° 20 and 22.22.

One end side of one rotating shaft 24 is connected to the side wall 14 of the housing 12.
The other end of the rotating shaft 24 and the same side of the rotating shaft 26 are both I! l? It stands out from the i-18. A pulley 28 that is operatively connected to an engine or the like via a belt (not shown) is fixed to the end of the rotating shaft 24 protruding from the side wall 14, and the rotating shaft 24 is rotated by the driving force applied to this pulley 28. It is designed to be rotationally driven. Also, the partition wall 18 of the rotating shaft 24.26
Timing gears 30 and 32 having the same number of teeth and meshing with each other are fixed to the ends protruding from the rotating shaft 24.
As the rotary shaft 2G is driven, the rotating shaft 2G is rotated in the opposite direction at the same speed.

The parts of the rotating shafts 24 and 26 located inside the rotor chamber 16 have a central hole 36 formed in the center of each of the cocoon-shaped rotors 10 and 10 having the same shape and having a pair of blades 34 having a circular outer shape. They are press-fitted with a phase difference of 90° between them, and rotate in opposite directions as the rotating shafts 24 and 26 rotate. and,
By the rotation of the cocoon-shaped rotors 10, 10, the air sucked into the rotor chamber 16 from the suction port 38 is forced to be sent toward the engine from the discharge port 40, as shown by the arrow in FIG. There is.

By the way, in such a supercharger, it is necessary to compress air so that the pressure at the discharge port 40 is approximately 9.5 kg/ad, and the pressure at the discharge port 40 is increased by this adiabatic compression and frictional heat generation of the mechanical parts. The temperature in that part reaches about 100-130'C. Also,
Correspondingly, the cocoon-shaped rotor 10 in the rotor chamber 16 also reaches approximately the same high temperature, and the side wall 14 and partition wall 18 that support the rotating shafts 24 and 26 of the housing 12 also rise to approximately the same temperature. Therefore, when the cocoon-shaped rotor 10 is manufactured only from steel, the amount of expansion in the radial direction of the cocoon-shaped rotor 10 is larger than the amount of expansion in the side wall 12 of the housing 12 at high temperatures.
The amount of expansion of the partition wall 18 becomes larger, and the clearance between the outer circumferential surfaces of the cocoon-shaped rotor 10 and between the outer circumferential surface of the cocoon-shaped rotor 10 and the inner circumferential surface of the housing 12 increases, and the volumetric efficiency of the supercharger increases. decreases. On the other hand, if the cocoon-shaped rotor 10 is made only of aluminum similar to the housing 12, the temperature of the cocoon-shaped rotor 10 will be higher than that of the side wall 14 and the partition wall 18 of the housing 12, so that both cocoon-shaped rotor 10 and There is a risk that interference will occur between the rotor 10 and the housing 12, and if this is avoided, the problem arises that the clearance between the rotors 10 and the housing 12 increases during medium to low temperatures, resulting in a decrease in volumetric efficiency.

Therefore, in this embodiment, the cocoon-shaped rotor 10 is configured as shown in FIGS. 1 and 2.

That is, in those figures, 42 is a rotor body made of aluminum similar to the housing 12, and the pair of blades 34 are connected from a thick boss portion 43 in which the center hole 36 is formed in the center. are shaped so that they extend toward opposite sides. And those feathers 34
A through hole 44 having a circular cross section whose center line is a straight line that is parallel to the rotation center line of the rotor 10 and spaced a certain distance from the center of the circular outer portion of each blade 34 on the side opposite to the rotation center line of the rotor 10. are formed in each of these through holes 44, and a steel material having a coefficient of thermal expansion of about 1.0 to 1.2 x 10-'/''C, which is sufficiently small compared to that of aluminum, and a Young's modulus sufficiently large compared to that of aluminum, is used. An inner piece 46 in the shape of an equal inner cylinder is press-fitted with a predetermined tightening margin.As a result, the value obtained by dividing the wall thickness of the peripheral wall portion 48 of the blade 34 by the wall thickness of the inner piece 46 is
34 blades each.

, it is smallest at the tip farthest from the rotation center line of the rotor 100, and becomes larger as it moves away from there.

In such a cocoon-shaped rotor 10, the circumferential wall portion 48 of the blade 34 is elastically deformed by press-fitting the inner piece 46 into the through hole 44, thereby determining the radial dimension of the cocoon-shaped rotor 10.

Therefore, when the temperature of the rotor 10 rises, both the inner piece 46 and the peripheral wall 48 of the blade 34 expand thermally. The amount of thermal expansion of the blade 46 becomes smaller than the amount of thermal expansion of the peripheral wall 48 of the blade 34, and the elastic expansion of the peripheral wall 48 is alleviated by that amount. Therefore, the amount of expansion in the radial direction of each blade 34 of the cocoon-shaped rotor 10 is smaller than when the inner piece 46 is not press-fitted. That is, by press-fitting the inner piece 46 into the through hole 44 formed in each blade 34, the substantial coefficient of thermal expansion in the radial direction of each blade 34 is made smaller than that of aluminum.

Further, the substantial thermal expansion coefficient of each part of each blade 34 becomes smaller as the value obtained by dividing the thickness of the peripheral wall 48 of the blade 34 at each part by the thickness of the inner piece 46 becomes smaller. Therefore, as is clear from FIG. 1, the inner piece 46
The effective coefficient of thermal expansion is the smallest in the radial direction extending from the center of the rotor 10 in the direction opposite to the rotational center line of the rotor 10, and the effective coefficient of thermal expansion becomes larger in the radial direction where the angle with the radial direction is larger. Accordingly, the substantial coefficient of thermal expansion in each direction extending radially from the rotation center line of the rotor 10 also differs from the rotation center line of the rotor 10 to each blade 3.
It is smallest in the straight line direction passing through the center of the circular outer portion of No. 4 (hereinafter, this direction is simply referred to as the longitudinal direction), and becomes larger in the direction where the angle formed with the longitudinal direction is larger.

On the other hand, the distance from the rotation center of the cocoon-shaped rotor 10 to the outer circumferential surface of the cocoon-shaped rotor 10 in the direction extending radially is longest in the longitudinal direction of the rotor 10, and is shorter in the direction where the angle formed with the longitudinal direction becomes larger. Become.

In other words, in the cocoon-shaped rotor 10 of this embodiment, in each direction extending radially from the center line of rotation, the effective coefficient of thermal expansion is made smaller in the longer distance, and as a result, the coefficient of thermal expansion decreases in each direction when the temperature rises. The substantial amount of expansion in the radial direction is made to be as large as possible in all radial directions. In this embodiment, the center position of the through hole 44 is set so that the substantial amount of expansion in each radial direction corresponds as much as possible to 1/2 of the amount of thermal expansion of the interaxial distance between the cocoon-shaped rotors 10. , the wall thickness of the inner piece 46 , the tightening margin, etc. are set in advance, and the total rotational phase of the rotor 10 and the housing 1 are determined in advance.
The clearance between the two rotors 10 is kept as constant as possible over the entire temperature change range within the rotor 2, and the clearance is made as small as possible to the extent that the two rotors 10 do not interfere with each other. The clearance between them is always kept as small as possible.

Note that the substantial thermal expansion coefficient in the longitudinal direction of the cocoon-shaped rotor 10 is determined by the amount of thermal expansion on one side in the longitudinal direction from the portions of the side wall 14 of the housing 12 and the partition wall 18 that support the rotating wheels 24 and 26 to those side walls. 14 and bulkhead 18
This is preset to match as much as possible the amount of thermal expansion up to the outer peripheral edge of the housing 1
Regardless of temperature changes within the housing 12, the clearance between the inner circumferential surface of the housing 12 and the outer circumferential surface of the rotor 10 is made as small as possible to the extent that they do not interfere with each other.

As explained above, in the supercharger equipped with the cocoon-shaped rotor 10 of this embodiment, regardless of the temperature inside the housing 12 and the change in the rotational phase of the rotor 10, both rotors 10 and each rotor 10 and the housing 12 Since the clearance between the two rotors 10 and the housing 12 can be maintained at a small, almost constant value, there is no interference between the two rotors 10 and the housing 12 (and the volumetric efficiency of the supercharger can always be maintained at a high level).

Next, another embodiment of the present invention is shown in FIG. In this embodiment, as is clear from the figure, the center of the through hole 50 coincides with the center of the circular outer diameter portion of each blade 34, and there is a portion inside the through hole 50 (close to the rotation center line of the rotor 10). jl,!1
A refined inner piece 52 with a thinner throat wall thickness is press-fitted with a predetermined tightening margin. Even in such a cocoon-shaped rotor, the peripheral wall portion 48 of each blade 34 in the radial direction
In which direction is the value obtained by dividing the wall thickness of the inner piece 52 by the wall thickness of the inner piece 52 smallest in the radial direction extending from the center of each blade 34 in the direction opposite to the rotation center of the rotor, and the angle formed with that direction is large? As the size increases, the difference in the amount of thermal expansion in each direction extending radially from the rotational center line of the rotor is reduced, and therefore the clearance between the two rotors is almost constant regardless of the rotational phase of the rotor and temperature changes inside the housing 12. vinegar sauce to the size of the dish. Therefore, by setting the substantial coefficient of thermal expansion of the rotor in the longitudinal direction and the amount of thermal expansion of each rotor in the radial direction in the same manner as in the embodiment described above, the same effects as in the embodiment described above can be obtained.

Further, FIG. 6 shows still another embodiment of the present invention. In this embodiment, a steel inner piece 54 having a thick circular arc portion on the side opposite to the rotational center line of the rotor is placed in a through hole 50 having a center similar to that of the embodiment shown in FIG. It is press-fitted with a tightening allowance of . Even in such a cocoon-shaped rotor, the value obtained by dividing the wall thickness of the peripheral wall portion 48 in the radial direction of each blade 34 by the wall thickness of the inner piece 54 is the value of each blade 34.
Thermal expansion is smallest in the radial direction extending from the center of the rotor in the direction opposite to the rotation center of the rotor, and becomes larger in the direction that makes a larger angle with that direction, so thermal expansion in each direction radially extending from the rotor's rotation center line The volumetric efficiency of the supercharger is thus maintained high without interference between the rotors and the housing 12 over the entire range of temperature changes within the housing 12 and during all rotational phases of the rotor. This is possible.

Although several embodiments of the present invention have been described above, these are literally illustrative, and the present invention should not be construed as being limited to these specific examples.

For example, in the embodiment described above, all the inner pieces were made of steel and their Young's modulus was larger than that of the rotor body, so the amount of shrinkage of the inner pieces during press-fitting was small, and the blades 34 This has the advantage that the peripheral wall portion 48 of the inner piece is effectively expanded and the amount of thermal expansion of the cocoon-shaped rotor 10 at high temperatures can be suppressed to a relatively small amount. It doesn't have to be larger than the main body (
, and does not necessarily have to be made of steel. In short, the inner piece only needs to have a coefficient of thermal expansion smaller than that of the rotor body.

Further, in the above embodiment, the inner piece was press-fitted over the entire length of the through-hole, but the inner piece does not necessarily have to be press-fitted over the entire length of the through-hole, and the inch pieces are press-fitted only at both ends of the through-hole in the axial direction. At the same time,
When the inner piece is press-fitted at low temperatures, the outer diameter of the circular outer portion of the blade 340 is constant over the entire length, and at high temperatures, the amount of expansion at the axial center of the cocoon-shaped rotor 10 is greater than that at both axial ends. It may be made larger. Since the temperature of the housing 12 rises to almost the same level as the rotor 10 at the center of the wall facing the outer peripheral surface of the cocoon-shaped rotor 10, the amount of expansion at the center of the rotor 10 is made smaller than that at both ends. If it is made larger, the clearance between the cocoon-shaped rotor 10 and the housing 12 is kept approximately constant throughout the entire axial direction of the rotor 10.

This makes it possible to maintain the volumetric efficiency of the supercharger even higher. In addition, in the center of the through hole, there is a 1. A similar effect can be obtained by press-fitting another inner piece made of a material with a larger coefficient of thermal expansion.

In addition, in the above explanation, all inner pieces have blade 3.
Although the inner piece has been described as being press-fitted into the M through hole formed in 4, the inner piece may be tightly fitted by other means such as shrink fitting or cold fitting.

Although not listed here, it goes without saying that the present invention can be practiced with various modifications and improvements without departing from the spirit thereof.

[Brief explanation of the drawing]

FIG. 1 is a front sectional view showing a cocoon-shaped rotor according to an embodiment of the present invention, and FIG. 2 is a sectional view taken along line II-[1]. FIG. 3 is a front sectional view showing the supercharger equipped with the cocoon-shaped rotor shown in FIG. 1, and FIG.
FIG. 5 and 6 are views corresponding to FIG. 1, respectively, showing other embodiments of the present invention. 10: Cocoon-shaped rotor 12: Housing 24.26:
Rotating shaft 34: Blade 42: Rotor body 44.50: Through hole 46.52
, 54: Inch piece 48 two peripheral walls

Claims (1)

[Claims] A supercharger that supercharges air to an engine by rotating a pair of cocoon-shaped rotors made of aluminum and each having two blades in opposite directions at the same speed within an aluminum housing. a cocoon-shaped rotor used in A cylindrical inner piece made of A cocoon-shaped rotor for a supercharger, characterized in that the rotor is smallest at a farthest part and becomes larger as it moves away from that part.